1. Field of the Invention
The present invention relates to the antigen used to elicit immune response, more particularly, relates to the polypeptide antigen against Acinetobacter baumannii. The present invention further relates to the vaccine composition comprising the polypeptide antigen against Acinetobacter baumannii and the antibody specifically bound to the polypeptide antigen of Acinetobacter baumannii. Moreover, the present invention relates to the isolated nucleic acid encoding the polypeptide antigen of Acinetobacter baumannii, the expression vector containing the isolated nucleic acid, and the host cell containing the expression vector.
2. The Prior Arts
Acinetobacter spp. are widely distributed in nature. They are gram-negative bacteria and are approximately divided into 20 species. Among them, Acinetobacter baumannii is the most general and well-studied. They can survive on a variety of surfaces, whether wet or dry, and have become one of the most common nosocomial pathogens in the hospital. Acinetobacter baumannii is an opportunistic human pathogen. Normally, it is nonpathogenic to a healthy individual, while it would cause severe clinical disease when the individual is with compromised immune systems.
In general, Acinetobacter baumannii is found on various objects or devices in a hospital, such as gloves, syringes, needles, carts, respirators, beds, cabinets, sinks, floor, and outlets of air conditioner, even in a stethoscope or medical records. Particularly, Acinetobacter baumannii often appears in the warm and humid environments such as drinking water, food, and drainage channels as well as in/on the human body, such as skin, armpits, conjunctiva, oral cavity, upper respiratory tract, nasopharynx, gastrointestinal tract, urethra, etc. The patients or their families contacted with these bacteria are generally got sick when their immune system becomes weak. In particular, during invasive treatments such as intubation or surgery, the patients would have higher risk been infected by these opportunistic pathogens. Thus, the probability of nosocomial infection has increased and thus become a serious health problem concerning the patients and the health care.
Generally, antibiotics are usually used for the treatment of bacterial infection. However, due to the overuse of antibiotics, some bacteria gradually become resistant to which and are difficult to eliminate. The way to overcome this problem is to treat with different antibiotics or apply new but expensive antibiotics. If there is no effective way to inhibit the evolution of resistance of bacteria to drugs, no available antibiotics for curing the bacterial infection will arrive in the near feature. Regarding Acinetobacter baumannii which causes nosocomial infections, many multi-drug resistant strains thereof have been isolated. Since they can survive for some time on the surface of an object, there is a need to provide a proper treatment or prevention method so that the problem of nosocomial infection can be reduced.
To vaccinate subjects to generate the protection against bacterial infection may be an effective way to solve the problem described above. Most vaccines are produced by inactivated or attenuated pathogens and then the whole treated pathogens are injected into an individual. The immunized individual responds by producing both a humoral (i.e., antibody) and cellular (i.e., cytotoxtic, helper or regulatory T cell) response, thereby the pathogen invading a host later can be neutralized and cleared. However, the use of attenuated or inactivated pathogen vaccines for the prevention of diseases may be dangerous, especially when the pathology and attenuation nature thereof are not clear. Thus, a vaccine composition comprising the antigens of pathogen epitopes which can stimulate an immune response, rather than introducing the whole pathogen, is currently one of the main methods for preparation of safer vaccines.
However, identification of specific antigens to prepare the vaccine is difficult. In previous studies, Pantophlet et al. has identified Acinetobacter strains by lipopolysaccharide O antigen and corresponding antibodies (Pantophlet R. et al., Clinical and Diagnostic Laboratory Immunology, 9, 60-65, 2002), but which have not disclosed other antigens and any vaccine applications thereof. Although U.S. Pat. No. 6,562,958 has disclosed about 4000 nucleotide and amino acid sequences relating to Acinetobacter baumannii, however, they are mostly with unidentified function and whether the gene can be expressed or not is unknown. Therefore, to prevent and diagnose Acinetobacter baumannii infection, there is an urgent need to find the target antigens to elicit immune response efficiently and specific antibodies used in diagnostic and treatment of Acinetobacter baumannii infection.